High-K Metal Gate CMOS

ABSTRACT

A method of forming a semiconductor device is provided that includes forming a Ge-containing layer atop a p-type device regions of the substrate. Thereafter, a first dielectric layer is formed in a second portion of a substrate, and a second dielectric layer is formed overlying the first dielectric layer in the second portion of the substrate and overlying a first portion of the substrate. Gate structures may then formed atop the p-type device regions and n-type device regions of the substrate, in which the gate structures to the n-type device regions include a rare earth metal.

FIELD OF THE INVENTION

The present disclosure relates to gate structures in metal oxidesemiconductor field effect transistors.

BACKGROUND OF THE INVENTION

Field effect transistors (FETs) are widely used in the electronicsindustry for switching, amplification, filtering and other tasks relatedto both analog and digital electrical signals. Most common among theseare metal oxide semiconductor field effect transistors (MOSFET or MOS),in which a gate structure is energized to create an electric field in anunderlying channel region of a semiconductor body, by which electronsare allowed to travel through the channel between a source region and adrain region of the semiconductor body. Complementary MOS (CMOS) deviceshave become widely used in the semiconductor industry, wherein bothn-type and p-type (NMOS and PMOS) transistors are used to fabricatelogic and circuitry.

Continuing trends in semiconductor device manufacturing include areduction in electrical device feature size (scaling), as well asimprovements in device performance in terms of device switching speedand power consumption. Recent MOS and CMOS transistor scaling effortshave focused on high-k dielectric materials having dielectric constantsgreater than that of SiO₂ (e.g., greater than about 3.9), which can beformed in a thicker layer than scaled SiO₂, and yet which produceequivalent field effect performance. Another type of CMOS device that isavailable is one where the gate electrode includes at least a metallayer beneath a Si-containing, e.g., polysilicon, gate electrode.

SUMMARY OF THE INVENTION

A semiconductor device is provided that includes a substrate including afirst device region and a second device region; an n-type conductivitydevice present in the first device region including a first gatestructure having at least a first high-k dielectric and at least onerare earth metal present atop the first high-k dielectric; and a p-typeconductivity device present in the second device region including asecond gate structure having a second high-k dielectric, the second gatestructure atop a device channel including a Ge-containing layer, whereinthe second high-k dielectric has a greater positive charge than thefirst high-k dielectric.

A semiconductor device may also be provided that includes a substratehaving a first portion composed of semiconductor devices each having agate structure including a gate dielectric of a first thickness, and asecond portion composed of a semiconductor devices each having a gatestructure including a gate dielectric of a second thickness, wherein thesecond thickness is greater than the first thickness; n-type deviceregions present in each of the first portion and the second portion ofthe substrate, the semiconductor devices present in the n-type deviceregions including a gate structure composed of at least one rare earthmetal; and p-type device regions present in each of the first portionand the second portion of the substrate, the semiconductor devicespresent in the p-type device regions comprising a device channelincluding a Ge-containing layer.

In another aspect, a method of forming a semiconductor device isprovided that includes providing a substrate having p-type deviceregions and n-type device regions; forming a Ge-containing layer atopthe p-type device regions of the substrate, wherein the Ge-containinglayer is not present in the n-type device regions; forming a firstdielectric layer overlying the p-type device regions and the n-typedevice regions; removing the first dielectric layer from a first portionof the substrate including at least one of the p-type device regions andat least one of the n-type device regions, wherein a remaining portionof the first dielectric layer is present in a second portion of thesubstrate; forming a second dielectric layer having a thickness lessthan the first dielectric layer overlying the first dielectric layer inthe first portion of the substrate and atop the second portion of thesubstrate; and forming gate structures atop the p-type device regionsand the n-type device regions, the gate structures to the n-type deviceregions including a rare earth metal.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example and notintended to limit the invention solely thereto, will best be appreciatedin conjunction with the accompanying drawings, wherein like referencenumerals denote like elements and parts, in which:

FIG. 1 depicts a side cross-sectional view of an initial structure asused in one embodiment of the present invention, in which the initialstructure includes a substrate having p-type device regions and n-typedevice regions each having an upper surface with a hardmask dielectriclayer present thereon.

FIG. 2 depicts a side cross-sectional view of forming a first etch maskoverlaying the n-type device regions.

FIG. 3 depicts a side cross-sectional view of removing the hardmaskdielectric layer from the p-type device regions, in accordance with oneembodiment of the present invention.

FIG. 4 depicts a side cross-sectional view of one embodiment of forminga Ge-containing layer atop the p-type device regions of the substrate,wherein the Ge-containing layer is not present in the n-type deviceregions, in accordance with the present invention.

FIG. 5 depicts a side cross-sectional view of one embodiment of removinga remaining portion of the hardmask dielectric layer from the n-typedevice regions, in accordance with the present invention.

FIG. 6 depicts a side cross-sectional view of one embodiment of forminga first dielectric layer overlying the p-type device regions and then-type device regions, in accordance with the present invention.

FIG. 7 depicts a side cross-sectional view of forming a second etch maskover a second portion of the substrate.

FIG. 8 depicts a side cross-sectional view of removing the firstdielectric layer from a first portion of the substrate including atleast one of the p-type device regions and at least one of the n-typedevice regions, wherein a remaining portion of the first dielectriclayer is present in a second portion of the substrate, in accordancewith the present invention.

FIG. 9 depicts a side cross-sectional view of one embodiment of forminga second dielectric layer overlying the first dielectric layer in thefirst portion of the substrate and overlying the second portion of thesubstrate, in accordance with the present invention.

FIG. 10 depicts a side cross-sectional view of forming a rare earthmetal layer on the substrate.

FIG. 11 depicts a side cross-sectional view of forming a third etch maskthat protects the portion of the rare earth metal that is overlying then-type device regions.

FIG. 12 depicts a side cross-sectional view of removing the rare earthmetal layer from the p-type device regions.

FIG. 13 depicts a side cross-sectional view of blanket depositing a gatemetal layer over the structure depicted in FIG. 12.

FIG. 14 depicts a side cross-sectional view of forming gate structuresatop the p-type device regions and the n-type device regions, in whichthe gate structures to the n-type device regions include a rare earthmetal, in accordance with one embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed embodiments of the present invention are disclosed herein;however, it is to be understood that the disclosed embodiments aremerely illustrative of the invention that may be embodied in variousforms. In addition, each of the examples given in connection with thevarious embodiments of the invention is intended to be illustrative, andnot restrictive. Further, the figures are not necessarily to scale, somefeatures may be exaggerated to show details of particular components.Therefore, specific structural and functional details disclosed hereinare not to be interpreted as limiting, but merely as a representativebasis for teaching one skilled in the art to variously employ thepresent invention.

The embodiments of the present invention relate to novel methods offorming complementary metal oxide semiconductor (CMOS) devices. In oneembodiment, the present invention provides a low threshold voltage CMOSdevice, which may include features such as, but are not limited tointegration of thick dielectric layers suitable for analog devices, SiGeband gap engineering to provide low threshold voltage p-type devices,and the application of rare earth metals in the gate structures of lowthreshold voltage n-type devices. When describing the methods, thefollowing terms have the following meanings, unless otherwise indicated.

As used herein, “semiconductor device” refers to an intrinsicsemiconductor material that has been doped, i.e., into which a dopingagent has been introduced, giving it different electrical propertiesthan the intrinsic semiconductor. Doping involves adding dopant atoms toan intrinsic semiconductor, which changes the electron and hole carrierconcentrations of the intrinsic semiconductor at thermal equilibrium.

An “analog device” is a device that has been designed to realize analogfunctions, wherein in analog functions output signal followscontinuously input signal.

“Digital devices” as used herein, are devices and circuits designed torealize digital (computational) functions, wherein in digital systemsoutput signal in response to the input signal is either “on” or “off”.

As used herein, the term “conductivity type” denotes a semiconductorregion being p-type or n-type.

As used herein, “p-type” refers to the addition of impurities to anintrinsic semiconductor that create deficiencies of valence electrons,such as boron, aluminum, gallium or indium to an intrinsic semiconductorsubstrate.

As used herein, “n-type” refers to the addition of impurities thatcontribute free electrons to an intrinsic semiconductor, such asantimony, arsenic or phosphorous to a semiconducting substrate.

A “gate structure” means a structure used to control output current(i.e., flow of carriers in the channel, e.g., turn “on” or “off”) of asemiconductor device through electrical or magnetic fields.

As used herein, “threshold voltage” is the lowest attainable voltagethat will turn on a transistor.

As used herein, the term “device channel” is the region underlying thegate structure and between the source and drain of a semiconductordevice that becomes conductive when the semiconductor device is turnedon.

As used herein, the term “drain” means a doped region in semiconductordevice located at the end of the channel, in which carriers are flowingout of the semiconductor device through the drain.

As used herein, the term “source” is a doped region in the semiconductordevice, from which the majority carriers are flowing into the channel.

As used herein, the term “dielectric” denotes a non-metallic materialhaving a room temperature conductivity of less than about 10⁻¹⁰(Ω−m)⁻¹.

A “high-k” dielectric is a dielectric material having a dielectricconstant of 3.9 or greater.

As used herein, “conductive” denotes a room temperature conductivity ofgreater than about 10⁻⁸(Ω−m)⁻¹.

“Rare earth elements”, “alkaline earth metal”, and “rare earth metals”as used herein include the rare earth elements that are composed of thelanthanide and actinide series of the Periodic Table of Elements.

The “Lanthanide Series” includes lanthanum, cerium, praseodymium,neodymium, promethium, samarium, europium, gadolinium, terbium,dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

The “Actinium Series” includes thorium, protactinium, uranium,neptunium, plutonium, americium, curium, berkelium, californium,einsteinium, fermium, mendelevium, nobelium, and lawrencium.

The terms “overlying” or “atop”, “positioned on” or “positioned atop”,“underlying”, “beneath” or “below” mean that a first element, such as afirst structure, e.g., a first layer, is present on a second element,such as a second structure, e.g. a second layer, wherein interveningelements, such as an interface structure, e.g. interface layer, may bepresent between the first element and the second element.

The term “direct physical contact” or “abutting” means that a firstelement, such as a first structure, and a second element, such as asecond structure, are connected without any intermediary conducting,insulating or semiconductor layers at the interface of the twomaterials.

For purposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the invention, as it is oriented inthe drawing figures.

References in the specification to “one embodiment”, “an embodiment”,“an example embodiment”, etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

FIGS. 1-14 depict one embodiment of a method of forming a semiconductordevice 100 that includes providing a substrate 5 having p-type deviceregions 20 and n-type device regions 10 and forming a Ge-containinglayer 30 atop the p-type device regions 20 of the substrate 5, whereinthe Ge-containing layer 30 is not present in the n-type device regions10. In a following process step, a first dielectric layer 40 is formedatop the p-type device regions 20 and the n-type device regions 10.Thereafter, the first dielectric layer 40 is removed from a firstportion 50 of the substrate 5 including at least one of the p-typedevice regions 20 and at least one of the n-type device regions 10,wherein a remaining portion 40′ of the first dielectric layer is presentin a second portion 60 of the substrate 5. A second dielectric layer 70having a greater dielectric constant than the first dielectric layer isthen formed atop the remaining portion 40′ of the first dielectric layer40 in the second portion 60 of the substrate 5 and atop the firstportion 50 of the substrate 5. Thereafter, gate structures 80 a, 80 b,80 c, 80 d are formed atop the p-type device regions 20 and the n-typedevice regions 10, wherein the gate structures 80 a, 80 b, 80 c, 80 d tothe n-type device regions 10 include a layer of a rare earth metal 75.The above described method, as well as structures produced by theabove-described method are now described in greater detail.

FIG. 1 depicts one embodiment of a substrate 5 having p-type deviceregions 20 and n-type device regions 10, in which the upper surface ofthe substrate 5 in each of the p-type device regions 20 and the n-typedevice regions 10 have a hardmask dielectric layer 6 present thereon.The terms “p-type device regions” 20 and “n-type device regions” 10 meanthat the source and drain regions to the subsequently formedsemiconductor devices to the p-type device regions 20 are doped withp-type dopants, and the source and drain regions to the subsequentlyformed semiconductor devices to the n-type device regions 10 are dopedwith n-type dopants.

The substrate 5 may be any silicon containing substrate including, butnot limited to Si, bulk Si, single crystal Si, polycrystalline Si, SiGe,amorphous Si, silicon-on-insulator substrates (SOI), SiGe-on-insulator(SGOI), strained-silicon-on-insulator, annealed poly Si, and poly Siline structures. In one embodiment, when the substrate 5 is asilicon-on-insulator (SOI) or SiGe-on-insulator (SGOI) substrate, thethickness of the semiconducting Si-containing layer atop the buriedinsulating layer (not shown) may be 10 nm or greater. In one embodiment,the SOI or SGOI substrate may be fabricated using a thermal bondingprocess, or alternatively be fabricated by an ion implantation process,such as separation by ion implantation of oxygen (SIMOX).

The substrate 5 may also include an isolation region 13 separating thesemiconductor portion of the n-type device regions 10 from the p-typedevice regions 20. In one embodiment, the isolation regions 13 may alsoseparate, i.e., electrically isolate, other devices that are present onthe substrate. In one embodiment, the isolation region 13 is formed byetching a trench in the substrate 5 utilizing a dry etching process,such as reactive-ion etching (RIE) or plasma etching, and then fillingthe trench with an insulating material, such as an oxide. In oneembodiment, the trench may be filled using a deposition method, such aschemical vapor deposition (CVD).

The hardmask dielectric layer 6 may be a nitride, an oxide, and/oroxynitride material. Some examples of materials for the hardmaskdielectric layer 6 include, but are not limited to SiO₂, Si₃N₄, SiON,boron phosphate silicate glass, Al₂O₃, HfO₂, ZrO₂, HfSiO, or anycombination thereof. Typically, the hardmask dielectric layer 6 may havea thickness ranging from 1 nm to 500 nm. In another embodiment, thehardmask dielectric layer 6 has a thickness ranging from 50 nm to 450nm. The hardmask dielectric layer 6 may be deposited by chemical vapordeposition (CVD). Variations of CVD processes include, but not limitedto Atmospheric Pressure CVD (APCVD), Low Pressure CVD (LPCVD) and PlasmaEnhanced CVD (PECVD), Metal-Organic CVD (MOCVD) and combinationsthereof.

FIGS. 2 and 3 depict one embodiment of removing the hardmask dielectriclayer 6 from the p-type device regions 20. Referring to FIG. 2, thehardmask dielectric layer 6 may be removed from the p-type deviceregions 20 utilizing lithography and etching. For example, thelithographic step may include applying a photoresist to the hardmaskdielectric layer 6, exposing the photoresist to a pattern of radiationand developing the pattern into the exposed photoresist utilizing aresist developer to provide a first etch mask 7. The first etch mask 7may be a patterned photoresist present overlying the portion of thehardmask dielectric layer 6 that is atop at least the n-type deviceregions 10, wherein the portion of the hardmask dielectric layer 6 atopthe p-type device regions 20 is exposed, as depicted in FIG. 2. It isnoted that although the above-described embodiment utilizes a patternedphotoresist for the first etch mask 7 to remove the hardmask dielectriclayer 6 from the p-type device regions 20, in other embodiments of thepresent invention, a hardmask material, such as a dielectric, may besubstituted for the photoresist used to provide the first etch mask 7.

Referring to FIG. 3, the exposed portion of the hardmask dielectriclayer 6, i.e., the portion of the hardmask dielectric layer 6 overlyingthe p-type device regions 20, may then be removed using an etchingprocess, such as a selective etching process. As used herein, the term“selective” in reference to a material removal process denotes that therate of material removal for a first material is greater than the rateof removal for at least another material of the structure to which thematerial removal process is being applied. In one embodiment, theetching process includes, but is not limited to: wet etching, such asdilute HF or buffered HF, chemical reactive ion etching (RIE), plasmaetching, ion beam etching or laser ablation. Following etching, thefirst etch mask 7 is typically removed from the structure utilizing aresist stripping process, such as oxygen ashing, or a wet resist stripusing a mixture of sulfuric acid and peroxide.

FIG. 4 depicts one embodiment of forming a Ge-containing layer 30 atopthe p-type device regions 20 of the substrate 5, wherein theGe-containing layer 30 is not formed in the n-type device regions 10. Inone embodiment, the Ge-containing layer 30 provides the device channelof the subsequently semiconductor devices to the p-type device regions20. The Ge-containing layer 30 is typically composed of silicongermanium (SiGe). Typically, the Ge-containing layer 30 has a thicknessranging from 1 nm to 100 nm. In another embodiment, the Ge-containinglayer 30 has a thickness ranging from 20 nm to 80 nm. Suitable growthmethods for providing the Ge-containing layer 30 may include, but arenot limited to: selective epitaxial growth, molecular beam epitaxy(MBE), chemical beam epitaxy (CBE), chemical vapor deposition (CVD),plasma-enhanced chemical vapor deposition (PECVD) and ion-assisteddeposition.

In one embodiment, the Ge-containing layer 30 is formed using aselective deposition process, in which a semiconductor materialnucleates and deposits on a semiconductor surface, i.e., on the exposedsurface of the p-type device regions 20, e.g., a silicon containingsurface of the substrate 5 in the p-type device regions 20, while notdepositing on insulator surfaces. In one embodiment, the Ge-containinglayer 30 is not formed on the surface of the remaining portion of thehardmask dielectric layer 6 that is present in the n-type device regions10 of the substrate 5 and the surface of the isolation regions 13. Inone embodiment, selectivity of the deposition process may be provided byan etchant such as dichlorosilane, hydrogen chloride (HCl) in thereactant stream or by a germanium source, such as germane (GeH₄) ordi-germane (Ge₂H₆).

The Ge-containing layer 30 that is formed over the Si-containing surfaceof the substrate 5 in the p-type device regions 20 may be epitaxial orpolycrystalline depending on deposition conditions and surfacepreparation. In one embodiment, the deposition temperature is typicallyin the range from 450° C. to 1,000° C. In another embodiment, thedeposition temperature ranges from 600° C. to 900° C. Typical processpressure for Ge-containing layer 30 formation can range from 1 Torr to200 Torr.

FIG. 5 depicts one embodiment of removing the remaining portion of thehardmask dielectric layer 6 from the n-type device regions 10. The Gecontaining layer 30 is present in the p-type device regions 20 toprovide a work function adjustment that optimizes the subsequentlyformed pFETs. The remaining portion of the hardmask dielectric layer maybe removed by a selective etch process, in which the etch chemistryremoves the hardmask dielectric layer 6 selective to the underlyingsurface of the substrate 5 in the n-type device regions 10, theisolation regions 13, and the Ge-containing layer 30. In one example, inwhich the hardmask dielectric is composed of silicon oxide (SiO₂), theGe-containing layer 30 is composed of SiGe, and the isolation regions 13are composed of silicon oxide (SiO₂), the etch chemistry may includedilute HF or buffered HF.

FIG. 6 depicts one embodiment of forming a first dielectric layer 40overlying the p-type device regions 20 and the n-type device regions 10.The first dielectric layer 40 may be composed of an oxide, a nitrideand/or an oxynitride. The first dielectric layer 40 may be formed usingchemical vapor deposition, such as plasma enhanced chemical vapordeposition, or thermal growth. Typically, the first dielectric layer 40has a thickness from 1 nm to 10 nm. More typically, the first dielectriclayer 40 has a thickness from 1 nm to 4 nm.

FIGS. 7 and 8 depict removing the first dielectric layer 40 from a firstportion 50 of the substrate 5 including at least one of the p-typedevice regions 20 and at least one of the n-type device regions 10,wherein a remaining portion 40′ of the first dielectric layer is presentin a second portion 60 of the substrate 5. In one embodiment, theremaining portion 40′ of the first dielectric layer contributes to thegate dielectric thickness of subsequently formed analog devices. Thefirst dielectric layer 40 is removed from a first portion 50 of thesubstrate 5 using photolithography and etch processes. Morespecifically, a pattern is produced by applying a photoresist layer tothe surface to be etched, exposing the photoresist layer to a pattern ofradiation, and then developing the pattern into the photoresist layerutilizing a resist developer to provide a second etch mask 8. Once thesecond etch mask 8 is completed, the sections of the first dielectriclayer 40 covered by the second etch mask 8 are protected, while theexposed regions are removed using a selective etching process thatremoves the unprotected portion. In one embodiment, the etching processincludes, but is not limited to chemical reactive ion etching (RIE),plasma etching, ion beam etching or laser ablation. In one embodiment,in which the first dielectric layer 40 is composed of silicon oxide(SiO₂), the substrate 5 is composed of silicon (Si) and theGe-containing layer 30 is composed of silicon germanium (SiGe), theexposed portion of the first dielectric layer 40 is removed using aselective etch process having an etch chemistry composed of dilute Hf orbuffered HF.

Following etching, the second etch mask 8 may be removed from thestructure utilizing a resist stripping process, such as oxygen ashing,or a wet resist strip using sulfuric acid and peroxide. It is noted thatalthough the above-described embodiment utilizes a patterned photoresistfor the second etch mask 8 to remove the first dielectric layer 40 fromthe first portion 50 of the substrate 5, in other embodiments of thepresent invention, a hardmask material, such as a dielectric, may besubstituted for the photoresist used to provide the second etch mask 8.

FIG. 9 depicts one embodiment of forming a second dielectric layer 70overlying the first dielectric layer 40′ in the second portion 60 of thesubstrate 5, and atop the upper surface of the first portion 50 of thesubstrate 5. In one embodiment, the second dielectric layer 70 providesthe gate dielectric thickness of subsequently formed digital devices inthe first portion 50 of the substrate 5.

In one embodiment, the second dielectric layer 70 is composed of ahigh-k dielectric material. The high-k dielectric material may becomposed of an insulating material having a dielectric constant ofgreater 4.0. In another embodiment, the high-k dielectric material has adielectric constant greater than 7.0. The high-k dielectric material mayinclude an oxide such as, for example, HfO₂, ZrO₂, Al₂O₃, TiO₂, La₂O₃,SrTiO₃, LaAlO₃, Y₂O₃ and mixtures thereof. Other examples of materialsfor the high-k dielectric material include hafnium silicate, hafniumsilicon oxynitride or combinations thereof.

The high-k dielectric material may be deposited by chemical vapordeposition (CVD). Chemical vapor deposition (CVD) is a depositionprocess in which a deposited species is formed as a result of a chemicalreaction between gaseous reactants at greater than room temperature,wherein solid product of the reaction is deposited on the surface onwhich a film, coating, or layer of the solid product is to be formed.Variations of CVD processes include, but are not limited to: Atomiclayer deposition, Atmospheric Pressure CVD (APCVD), Low Pressure CVD(LPCVD), Plasma Enhanced CVD (EPCVD), Metal-Organic CVD (MOCVD) andcombinations thereof. The high-k dielectric material may be depositedusing a conformal deposition method. The term “conformal” denotes alayer having a thickness that does not deviate from greater than or lessthan 20% of an average value for the thickness of the layer.

The second dielectric layer 70 typically has a thickness that is lessthan the first dielectric layer 40′. In one embodiment, in which thesecond dielectric layer 70 is composed of a high-k dielectric material,the second dielectric layer may have a thickness of less than 10 nm andgreater than 0.8 nm. More typically, the second dielectric layer 70 iscomposed of a high-k dielectric material has a thickness ranging from1.0 nm to 6.0 nm.

FIGS. 10-14 depict forming gate structures 80 a, 80 b, 80 c, 80 d atopthe p-type device regions 20 and the n-type device regions 10, in whichthe gate structures 80 a, 80 b, 80 c, 80 d to the n-type device regions10 include an alkaline earth metal-containing material or a rare earthmetal (or a rare earth-like).

Referring to FIG. 10, a layer of an alkaline earth metal-containingmaterial or a rare earth metal (or a rare earth-like) containingmaterial 75, hereafter collectively referred to as a rare earth metallayer 75, is formed atop at least the second dielectric layer 70 andoverlying the first dielectric layer 40′ that is present in the secondportion 60 of the substrate 5, and the second dielectric layer 70 thatis present in the first portion 50 of the substrate 5. The rare earthmetal layer 75 may be blanket deposited atop the upper surface of thestructure depicted in FIG. 9 including the upper surface of theisolation region 13. In one embodiment, the rare earth metal layer 75 iscomposed of a compound having the formula M_(x)A_(y), wherein M is analkaline earth metal (Be, Mg, Ca, Sr, and/or Ba), A is one of O, S or ahalide, x is 1 or 2, and y is 1, 2 or 3. In one embodiment, the presentinvention contemplates a rare earth metal layer composed of rare earthmetal compounds that include a mixture of alkaline earth metals and/or amixture of anions, such as —OCl₂. Examples of rare earth metal compoundsthat may be used in some embodiments of the present invention include,but are not limited to: MgO, MgS, MgF₂, MgCl₂, MgBr₂, MgI₂, CaO, CaS,CaF₂, CaCl₂, CaBr₂, CaI₂, SrO, SrS, SrF₂, SrCl₂, SrBr₂, SrI₂, BaO, BaS,BaF₂, BaCl₂, BaBr₂, and BaI₂. In one embodiment of the presentinvention, the rare earth metal layer 75 includes Mg. MgO is anotheralkaline earth metal-containing material that may be employed in therare earth metal layer 75. In another example, the rare earth metallayer 75 comprises an oxide or nitride of at least one element fromGroup IIIB of the Periodic Table of Elements including, e.g., La, Ce,Pr, Nd, Pm, Sm, Eu, Ga, Tb, Dy, Ho, Er, Tm, Yb, Lu or mixtures thereof.The rare earth metal layer 75 may also comprise an oxide of La, Ce, Y,Sm, Er, and/or Th. In one example, the rare earth metal layer 75 iscomposed of La₂O₃ or LaN.

The rare earth metal layer 75 may be formed utilizing a depositionprocess including, for example, sputtering from a target, reactivesputtering of an alkaline earth metal under oxygen plasma conditions,electroplating, evaporation, molecular beam deposition, MOCVD, ALD, PVDand other like deposition processes. The rare earth metal layer 75typically has a deposited thickness ranging from 0.1 nm to 3.0 nm. Inanother example, the rare earth metal layer 75 has a thickness from 0.3nm to 1.6 nm.

The presence of the rare earth metal layer 75 in the n-type deviceregions 10 provides a second dielectric layer 70 having a greaterpositive charge, i.e., the second dielectric is electropositive, thanthe first dielectric layer 40. The presence of the rare earth metal 75in the n-type device regions provides a work function shift thatoptimizes the nFETs. The electropositive element is utilized in thenFET, whereas the Ge-containing layer, i.e., SiGe layer, is present inthe pFET to provide independent work function adjustments to optimizeboth the pFET and the nFET.

Next, and as shown in FIG. 11, a third etch mask 9 is formed thatprotects the portion of the rare earth metal layer 75 that is overlyingthe n-type device regions 10 of the substrate 5, wherein the third etchmask 9 exposes the portion of the rare earth metal layer 75 that isoverlying the p-type device regions 20. The third etch mask 9 is formedusing similar materials and techniques as discussed above to provide thefirst etch mask 7 and the second etch mask 8, but may also include otherprocesses known to those skilled in the art. Following the formation ofthe third etch mask 9, etch process may be utilized to remove theexposed portion of the rare earth metal layer 75, i.e., the portion ofthe rare earth metal layer 75 that is overlying the p-type deviceregions 20 of the substrate 5, wherein the rare earth metal layer 75remains in the n-type device regions 10 of the substrate. Followingetch, the third etch mask 9 may be removed utilizing a strippingprocess.

FIG. 12 shows the structure that is formed after removing rare earthmetal layer 75 from within the pFET device regions 20.

Referring to FIG. 13, in a following process step, a gate metal layer 85is blanket deposited on the upper surface of the structure shown in FIG.12 utilizing a deposition process. Examples of deposition processes thatcan be used in forming the gate metal layer 85 include, but are notlimited to CVD, PVD, ALD, sputtering or evaporation. The gate metallayer 85 includes a metallic material that is capable of conductingelectrons. For example, the gate metal layer 85 may include a metalnitride or a metal silicon nitride. In one embodiment, the gate metallayer 85 is composed of a metal from Group IVB or VB of the PeriodicTable of Elements. Hence, the gate metal layer 85 may include, but isnot limited to: Ti, Zr, Hf. V, Nb, Ta or alloys thereof. In one example,the gate metal layer 85 comprises TiN or TaN. The physical thickness ofthe gate metal layer 85 may vary, but typically, the gate metal layer 85has a thickness ranging from 0.5 nm to 200 nm, with a thickness rangingfrom 5 nm to 80 nm being more typical.

In one embodiment of the present invention, the gate metal layer 85 isTiN that is deposited by evaporating Ti from an effusion cell held inthe range of 1550° C. to 1900° C., and using an atomic/excited beam ofnitrogen that is passed through a remote radio frequency source. The TiNmay be deposited, in other ways, as well, such as chemical vapordeposition or sputtering.

Still referring to FIG. 13, following the formation of the gate metallayer 85, a gate electrode 90 is formed atop the gate metal layer 85.Specifically, a blanket layer of a conductive material is formed on thegate metal layer 85 utilizing a deposition process, such as, forexample, physical vapor deposition, CVD or evaporation. The conductivematerial used as the gate electrode 90 includes, but is not limited toSi-containing materials such as Si or a SiGe alloy layer in eithersingle crystal, polycrystalline or amorphous form. The gate electrode 90may also be a conductive metal or a conductive metal alloy. Combinationsof the aforementioned conductive materials are also contemplated herein.Si-containing materials are suitable as the gate electrode (orconductor) 90, with polySi being most typical. In addition toaforementioned conductive materials, the present invention alsocontemplates instances wherein the conductor is fully silicided or astack including a combination of a silicide and Si or SiGe. In oneembodiment, fully silicided gates can be formed. The blanket layer ofgate electrode material may be doped or undoped. If doped, an in-situdoping deposition process may be employed in forming the same.Alternatively, a doped gate electrode 90 can be formed by deposition,ion implantation and annealing. The ion implantation and annealing canoccur prior to or after a subsequent etching step that patterns thematerial stack. The thickness, i.e., height, of the gate electrode 90may vary depending on the deposition process employed. Typically, thegate electrode 90 has a vertical thickness ranging from 20 nm to 180 nm,with a thickness ranging from 40 nm to 150 nm being more typical.

In a following process step, the gate stacks, i.e., gate structures 80a, 80 b, 80 c, 80 d are formed by lithography and etching of thematerial layers described above. The resultant structure that is formedafter gate stack formation is shown, for example, in FIG. 14. Followingpatterning of the material stack, at least one spacer (not shown) istypically, but not always, formed on exposed sidewalls of each patternedgas structure 80 a, 80 b, 80 c, 80 d. The at least one spacer iscomprised of an insulator, such as an oxide, nitride, oxynitride and/orany combination thereof. The at least one spacer is formed by depositionand etching. The width of the at least one spacer may be selected suchthat the source and drain silicide contacts (to be subsequently formed)do not encroach underneath the edges of the gate structures 80 a, 80 b,80 c, 80 d.

Source and drain dopant regions (not shown) are then formed into thesubstrate 5. The source and drain dopant regions are formed utilizingion implantation and an annealing step. The annealing step serves toactivate the dopants that were implanted by the previous implant step.The conditions for the ion implantation and annealing are well known tothose skilled in the art. The source/drain diffusion regions may alsoinclude extension implant regions, which are formed closer to the gatethan the source/drain implantation using a conventional extensionimplant. The extension implant may be followed by an activation anneal,or alternatively the dopants implanted during the extension implant andthe source/drain implant can be activated using the same activationanneal cycle. Halo implants are also contemplated herein. Further, CMOSprocessing such as formation of silicided contacts (source/drain andgate) as well as formation of BEOL (back-end-of-the-line) interconnectlevels with metal interconnects can be formed utilizing processing stepsthat are well known to those skilled in the art.

Still referring to FIG. 14, in one embodiment, the above-describedmethod produces a semiconductor device 100 including a substrate 5having a first device region 10 (interchangeably referred to as ann-type device region 10) and a second device region (interchangeablyreferred to as a p-type device region 20). In one embodiment, an n-typeconductivity device 110 a, 110 b is present in the first device region10 that includes a first gate structure 80 a having at least a firsthigh-k dielectric (provided by the second dielectric layer 70) and atleast one rare earth metal (provided by the rare earth metal layer 75)present atop the first high-k dielectric, and a p-type conductivitydevice 120 a, 120 b is present in the second device region 20 includinga second gate structure 80 b composed of a second high-k dielectric(provided by the second dielectric layer 70) that is present atop adevice channel composed of SiGe (provided by the Ge-containing layer30). In one example, the n-type conductivity device 110 a, 110 b is annFET having a work function ranging from 4.0 eV to 4.3 eV, and thep-type conductivity device 120 a, 120 b is a pFET having a 4.9 eV to 5.2eV.

At least one of the first high-k dielectric and the second high-kdielectric may be composed of HfO₂ or HfSiO_(x)N_(y), wherein the firsthigh-k dielectric and the second high-k dielectric may be composed ofthe same material. In another embodiment, the first high-k dielectricand the second high-k dielectric may be composed of a nitride-containinglayer.

In one embodiment, the first gate structure 80 a and the second gatestructure 80 b may include a metal gate conductor (also referred to agate metal layer 85), wherein the metal gate conductor of the first gatestructure 80 a is of a substantially same composition of the metal gateconductor of the second gate structure 80 b. For example, the metal gateconductor may be composed of TiN. The p-type conductivity device 120 mayfurther comprise a Si cap (not shown) overlying the device channelcomposed of SiGe. The rare earth metal may be composed of La, Ce, Pr,Nd, Pm, Sm, En, Ga, Tb, Dy, Ho, Er, Tm, Yb, Lu or alloys thereof.

In another embodiment, a semiconductor device 100 is provided thatincludes a first portion 50 of a substrate 5 composed of semiconductordevices each having a gate structure 80 c, 80 d including a gatedielectric of a first thickness and a second portion 60 of the substrate5 composed of semiconductor devices each having a gate structure 80 a,80 b including a gate dielectric of a second thickness, in which thesecond thickness is greater than the first thickness. The gatedielectric of the second thickness is typically provided by thecombination of the remaining portion of the first dielectric layer 40′and the second dielectric layer 70 that is present in the second portion60 of the substrate 5. The gate dielectric of the first thickness istypically provided by the second dielectric layer 70 that is present inthe first portion 50 of the substrate 5.

The semiconductor device 100 may further include n-type device regions10 that are present in each of the first portion 50 and the secondportion 60 of the substrate 5. The n-type device regions 10 may includesemiconductor devices having gate structures 80 a with gate dielectricsof the second thickness, and semiconductor devices having gatestructures 80 c with gate dielectrics of the first thickness, whereineach of the semiconductor devices in the n-type device regions 10include at least one rare earth metal.

The semiconductor device 100 may further include p-type device regions20 that are present in each of the first portion 50 and the secondportion 60 of the substrate 5. The p-type device regions 20 may includesemiconductor devices having gate structures 80 b with gate dielectricsof the first thickness, and semiconductor devices having gate structures80 d with gate dielectrics of the second thickness, wherein each of thesemiconductor devices in the p-type device regions 20 include a devicechannel composed of SiGe. In one embodiment, analog devices are presenthaving the gate dielectric of the first thickness, wherein digitaldevices are present having the gate dielectric of the second thickness.The analog devices may be present in the first portion 50 of thesubstrate 5, and the digital devices may be present in the secondportion 60 of the substrate 5.

In one embodiment, the gate dielectric of the first thickness rangesfrom 1 nm to 10 nm, typically ranging from 1 nm to 4 nm, and the gatedielectric to the second thickness ranges from about 1 nm to about 3 nm.The gate dielectric of the first thickness and the gate dielectric ofthe second thickness may be composed of an oxide.

In one embodiment, the above-described methods and structures provide ahigh performance, low threshold voltage CMOS device. In one example, theCMOS device may feature integration of devices incorporating thickdielectric structures that are suitable for analog applications incombination with the application of SiGe band engineering for lowthreshold voltage pMOS devices and the utilization of gate structurescomposed of rare earth metals for providing low threshold voltage nMOSdevices. The present integration scheme may also be applied to highperformance SRAM devices.

While the present invention has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present invention. It is therefore intended that the presentinvention not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

1. A semiconductor device comprising: a substrate comprising a firstdevice region and a second device region; an n-type conductivity devicepresent in the first device region comprising a first gate structurehaving at least a first high-k dielectric and at least one rare earthmetal present atop the first high-k dielectric; and a p-typeconductivity device present in the second device region comprising asecond gate structure having a second high-k dielectric, the second gatestructure atop a device channel including a Ge-containing layer, whereinthe second high-k dielectric has a greater charge than the first high-kdielectric.
 2. The semiconductor device of claim 1, wherein at least oneof the first high-k dielectric and the second high-k dielectriccomprises HfO₂ ZrO_(x), Al₂O₃ or HfSiO_(x)N_(y).
 3. The semiconductordevice of claim 1, wherein at least one of the first high-k dielectricand the second high-k dielectric comprises a nitride-containing layer.4. The semiconductor device of claim 1, wherein the first gate structureand the second gate structure include a metal gate conductor, whereinthe metal gate conductor of the first gate structure is of asubstantially same composition as the metal gate conductor of the secondgate structure.
 5. The semiconductor device of claim 4, wherein themetal gate conductor comprises TiN.
 6. The semiconductor device of claim7, wherein the p-type conductivity device further comprises a Si capoverlying the device channel composed of the Ge-containing layer.
 7. Thesemiconductor device of claim 1, wherein the rare earth metal comprisesLa, Ce, Pr, Nd, Pm, Sm, En, Ga, Tb, Dy, Ho, Er, Tm, Yb, Lu or alloysthereof.
 8. The semiconductor device of claim 1, wherein theGe-containing layer is SiGe.
 9. A semiconductor device comprising: asubstrate including a first portion composed of semiconductor deviceseach having a gate structure including a gate dielectric of a firstthickness, and a second portion composed of a semiconductor devices eachhaving a gate structure including a gate dielectric of a secondthickness, wherein the second thickness is greater than the firstthickness; n-type device regions present in each of the first portionand the second portion of the substrate, the semiconductor devicepresent in the n-type device regions including a gate structure composedof at least one rare earth metal; and p-type device regions present ineach of the first portion and the second portion of the substrate, thesemiconductor devices present in the p-type device regions comprising adevice channel including a Ge-containing layer.
 10. The semiconductordevice of claim 9, wherein the gate dielectric of the first thicknessranges from 1 nm to about 10 nm, and the gate dielectric of the secondthickness ranges from 1 nm to 3 nm.
 11. The semiconductor device ofclaim 9, wherein the semiconductor devices present in the first portionof the substrate are analog devices and the semiconductor devicespresent in the second portion of the substrate are digital devices. 12.The semiconductor device of claim 9, wherein the Ge-containing layer isSiGe.
 13. A method of forming a semiconductor device comprising: forminga Ge-containing layer atop p-type device regions of a substrate, whereinthe Ge-containing layer is not present in the n-type device regions ofthe substrate; forming a first dielectric layer atop the p-type deviceregions and the n-type device regions; removing the first dielectriclayer from a second portion of the substrate including at least one ofthe p-type device regions and at least one of the n-type device regions,wherein a remaining portion of the first dielectric layer is present ina first portion of the substrate; forming a second dielectric layeroverlying the first dielectric layer in the first portion of thesubstrate and overlying the second portion of the substrate; and forminggate structures atop the p-type device regions and the n-type deviceregions, the gate structures to the n-type device regions including arare earth metal.
 14. The method of claim 13, wherein the providing ofthe substrate having p-type device regions and n-type device regionsfurther comprises forming a hardmask dielectric layer at an uppersurface of each of the p-type device regions and the n-type deviceregions.
 15. The method of claim 13, wherein prior to the forming of theGe-containing layer atop the p-type device regions of the substrate, themethod further comprises forming an etch mask atop the n-type deviceregions that exposes the p-type device regions, etching the hardmaskdielectric layer in the n-type device regions to expose an upper surfaceof the substrate in the p-type device regions, and removing the etchmask.
 16. The method of claim 13, wherein the Ge-containing layer iscomposed of SiGe.
 17. The method of claim 16, wherein the forming of thefirst dielectric layer overlying the p-type device regions and then-type device regions comprises removing a remaining portion of thehardmask dielectric layer from the n-type device regions and depositingthe dielectric layer having a thickness ranging from about 1 nm to about10 nm.
 18. The method of claim 17, wherein the forming of the seconddielectric layer overlying the first dielectric layer in the secondportion of the substrate and overlying the first portion of thesubstrate comprises depositing a high-k dielectric material having athickness ranging from about 1 nm to about 3 nm.
 19. The method of claim17, wherein the forming gate structures atop the p-type device regionsand the n-type device regions comprises: depositing a rare earth metalatop the high-k dielectric material; removing the rare earth metal fromthe p-type device regions; forming a metal nitride layer overlying therare earth metal in the n-type device regions and atop the high-kdielectric material in the p-type device regions; and forming aSi-containing layer atop the metal nitride layer.
 20. The method ofclaim 17, comprising analog devices in the first portion of thesubstrate, and digital devices in the second portion of the substrate.